Figure 22.8 Compared to free-floating bacteria, bacteria in biofilms often show increased resistance to antibiotics and detergents. Why do you think this might be the case?
Figure 22.16 Which of the following statements is true?
- Gram-positive bacteria have a single cell wall anchored to the cell membrane by lipoteichoic acid.
- Porins allow entry of substances into both Gram-positive and Gram-negative bacteria.
- The cell wall of Gram-negative bacteria is thick, and the cell wall of Gram-positive bacteria is thin.
- Gram-negative bacteria have a cell wall made of peptidoglycan, whereas Gram-positive bacteria have a cell wall made of lipoteichoic acid.
Figure 22.19 Which of the following statements about the nitrogen cycle is false?
- Nitrogen fixing bacteria exist on the root nodules of legumes and in the soil.
- Denitrifying bacteria convert nitrates (NO3-) into nitrogen gas (N2).
- Ammonification is the process by which ammonium ion (NH4+) is released from decomposing organic compounds.
- Nitrification is the process by which nitrites (NO2-) are converted to ammonium ion (NH4+).